Felted material and method of manufacturing the same



Patented Aug. 18, 1931 lJNITED STATES PATENT OFFICE TREADWAY B. MUNROE AND ELBER'I' C. LATHROP,-OF CHICAGO, ILLINOIS; SAID LATHROP ASSIGNOR TO SAID MUNROE FELTED KATERIAL AND METHOD OF MANUFACTURING THE SAME No Drawing.

This invention relates to felted material and has for its object to provide such a material as well as a method of manufacturing the same which will be more eflicient in use and less costly than thoseheretofore proposed. With these and other objects in View the invention consists in the novel details of construction and combinations of parts constituting the article, and in the novel steps and combinations of steps constituting the method, all as will be more fully hereinafter disclosed and particularly pointed out in the claims.

This material is in a way comparable with ordinary felt and yet it differs therefrom quite considerably, is designed to have strength per given weight appreciably greater than that of ordinary felt, and which, while flexible, has a superior resiliency. In light weight say of a thickness 1/32 or 3/64 inch thick the material is quite flexible but it has a springiness and resiliency which ordinary felts do not have. As a comparison this material has a relation to the usual felts somewhat similar to that of hair cloth to a cotton'fabric,

and it is what We term semiflexible. Ingreater thickness say to 4 inch or more this material while flexible is what might be termed as semirigid, the springiness of the fibers of which this material is made and its resiliency make it, when compared with ordinary felt, seemingly rigid, thus in these greater thicknesses we term the material as semirigid.

While a particular object of this invention is the provision of a felted material for use as a linoleum flooring material in combination with a separate linoleum base which material is much superior to felt, it' is to be understood 4.0 that this material will have other uses suchas for carpet lining, sheathing paper, roofing felt and for similar applications. This felted material, when used under carpets, linoleums and other floor coverings comprises a relatively resilient base or sup ort, decreases wear of the floor covering, cus ions the foot steps, deadens sound, and retards transmission of heat and cold.

Prior to this invention substantially all cushioning of base materials used under floor Application filed November 19, 1928. Serial No. 320,530.

coverings have been felts or fibrous felts of a relatively soft spongy nature whereas as distinguished therefrom the material of this invention is, while light in weight, much more solid and rigid, in effect only, since the indi- 55 vidual fibers of which the material is made are very resilient of themselves.

Also prior to this invention building felts and papers, roofing felt base material and the like have comprised soft flaccid cotton, wool, '00 or cotton and wool felts or wood fiber felts in which the individual fibers are fine, short,

soft and relatively weak. As compared with past practice this invention contemplates using for a base material a felting fiber in which the individual fibers are rather finely divided but which fibers are comparatively long, resilient and strong. The felts made according to this invention have as other than their directly apparent advantages those of high initial heat insulation value, and particularly high absorptive values.

For a roofing material this product has particular advantages, it is more easilysaturated, it Will absorb a greater amountyof 78 saturant and as the material itself is stronger it is not ordinarily necessary to completely saturate it so that some advantage of its high heat insulation va ue can be realized. The raw material particularly preferred, so especially because of its availability for the manufacture of this new felted product, is bagasse, the fibrous residue remaining after expression of the juice from sugar cane. The

.invention is not to be understood as in any way limited to the use'of. bagasse only but includes any bagasse like fibrous materal of the cane family, particularly the stalks of the corns and sorghum and other members of the grass family as the primary raw material, the essential features being the preparation of the fiber and felting thereof as hereinafter described.

In the-manufacture of this felted material the first step is the production of fiber from the raw material. This raw material which will be hereafter referred to for clarity and uniformity as bagasse, is first subjected to digestion and refining whereby is produced a fiber suitable for the manufacture of the felted material of the invention.

The essential feature of this ste of the manufacture is that there be pro uced a fiber which for purposes of distinction. will be 5 termed a fiber not 'suitable for paper making.

These fibers are not the ultimate fibers referred to by the paper maker but they are rather fiber bundles or groups of fibers arranged and forming a tube-like structure.

By a. thorough digestion and refining there may be made from bagasse a fiber stock which is substantially disintegrated to elemental fibers and which is suitable for paper making, but such fiber is soft and not at all suited for use in the manufacture of the felted material of this invention since such fiber would produce a felt quite similar in characteristics to the usual felts.

Since, in so far as known, the most learned investigators are unable to definitely state the nature of the complexstructure of the fibrous vegetable materials or to agree exactly as to what happens, chemicall on digestion and refining of such materia s, no effort willbe made to so explain the invention chemically. The invention will be rather explained by its results, which, anyone skilled in the art can interpret.

Raw material, bagasse, which is already thoroughly crushed in the extraction of the sugar cane juice or by other suitable means is digested in water, as for example for one hour at a pressure of about 40 pounds per square inch. The time and pressure of di- 35 gestion will vary considerably depending on whether the bagasse is green, just from the cane mill, or whether the bagasse is aged, that is, has been stored for say two months to a year since crushing. The raw material may also be equally well digested in a caustic solution or may be prepared in any other manner known in the art so long as the resulting product is the fiber bundles to be described.

Practically all fibrous vegetation if out across and examined under a magnifying 'glass will be seen to be composed of numerous tubes extending lengthwise of the stem, these tube-like structures being arranged in some instances singly and in others as groups.

On such inspection there can also be noted the matter enerally known as pith, a mate rial which ls the s aces between 'and joins the fiber bundles. The fiber bundles, particularly the outer or shell fiber bundles, are encrusted or possibly permeated with a substance which renders them brittle.

The digestion and refining action to which the raw material is subjected is one by which 99 the fiber bundles are released from their binding and from at least part of their encrusting matters, whereby the relatively long, slender, flexible and resilient tubular fiber bunches r result either singly or in small groups. ,The digestion to obtain such result may be one such as previously mentioned as illustrative or may be any other form of digestion with, or without the use of chemicals producing the results desired. Digestion of fibrous materials is an art rather than a science and it is well known inthe art that any desired degree of digestion may be obtained equivalent to that desired by a water cook or by the variation of concentration of rated but that they not be cut and shortened.

Refining by pressure such as by passing the fiber mass thru heavy rolls or by wet shredding is probably preferably as vhaving the least cutting action but in some instances it is desirable tohave a certain amount of shortening or cuttin of the fibers in which case they may be refined in, or partly refined in, say a Jordan machine to obtain such effect after which the further refining may be in a machine of the other t pe.

Fibers of bagasse an the like prepared as above described comprise what is termed a free fiber that is, one which not only drains rapidly, but quickl gives Lup its moisture when subjected to rying. When a felt of such material is dried, due to the drying of the outer portions prior to drying of the inner portions, there is a tendency .to war To revent such warping a quantity 0 more nely divided and more highly hydrated fiber,

as close fiber (slow drying) is added to the free fiber, since it 'has been found that the inclusion of such fiber causes the entire mass to dry more uniformly and to prevent warpin This close fiber may be of the same origin as the free fiber excepting with further digestion and/or refining-to more highly hydrate it, or it, may be a different fiber altogether such as ground wood, sulphite pulp or its equivalent.

This relatively fine, close fiber, is not in its use to be in an wa compared to saw dust and the like or arily used in the manufacs ture of the-usual felts, particularly in roofing felt, as a filler. This fine fiber 1s of value not only in drying to cause the drying action to be more uniform, but these fine hydrated fibers-servev to tie together the coarser free fibers comprising the primary constituents of the felt. The constituent of the felt may be 100% to about 35% of the free fiber and 0% to65% close fiber, depending principally felted on a paper machine or the felt may be formed on a two roll,'or two wire, machine such as is shown, generally, in U. S. Patent 498,764. The specific type of machine on which the felt is formed is not of particular importance, since it would be possible to form the felt by other means such as the semi-dry process. The manner of the felting is of great importance in the process of manufacture of the felted material, and will be later described.

The felt sheet from the felting machine is compressed or squeezed to remove as much as possible of its water content without crushing the damp sheet. This partially water freed sheet then passes through a dryer from which it emerges in a more or less rigid board-like form depending largely of course upon its thickness, and whether it has been dried on heated cylinders, or passed through a heated tunnel.

Since a particular object of this invention is to provide a felted flooring material suitable for combinative use with a separate linoleum base, which is resilient yet which material does not have excessive give and which will not bunch or compact during and after use,.and one which will maintain its integrity through long use, a particular feature of the invention will now be described. It has been found that a material to serve as a linoleum base must have one characteristic in particular. It must preserve its integrity, that is, due to the fact that the linoleum is cemented to the upper surface of the base and that it is laid with but very little or no tacking, there is a constant tendency for the linoleum when walked on or upon the movement of any heavy object across its surface, to cause a separation of the base material along any horizontal cleavage planes which may exist. The base material must be uniformly and thoroughly felted, although if of a thickness say of ,4 or more, cleavage planes adjacent the lower face are not particularly objectionable if they are not too pronounced since the thickness of the'uniformly felted material thereabove serves as a protection and there is little or no tendency to cause cleavage in the planes adjacent the lower surface.

This thoroughly felted rather thick material may be formed on a single roll or single wire machine, but the rate of production would be rather low. The rate of production from a single machine can be more than doubled by employing a two roll or two wire machine and from an inspection of Patent 498,764 previously mentioned it can be readily seen why this is true. A felt will be formed on each wire, the two felts coming together at the. nip of the rolls. In addition to the fibers of the two felts it can be seen that a certain amount of fiber in suspension adjacent the nip of the rolls will be deposited between the approaching separately formed felts and the resultantemerging felt -will apparently be an integral sheet in amount equal to two or more times the production of a single roll or single wire machine. A felt formed on such a high production machine has been found unsuitable as a linoleum base due-to a certain amount of inherent weakness in the oining of the individual felts.

The disadvantage of the high production machine is overcome in this invention by incorporating into the process of production, as-an added step after the drying of the felt, a splitting machine. This splitting machine is of the type commonly employed in splitting leather and its general action is well known so that it need not be described. The purpose of this splitting machine is to divide the single felted sheet produced. into a plurality of thinner sheets which sheets are thoroughly or homogeneously felted and entirely free from lamination or horizontal cleavage planes excepting possibly one closely adjacent one of the surfaces, which sheets when used as linoleum base will be so laid that the possible cleavage plane will be on the under or floor side of the material.

The principle just described, of increased production may be applied in other ways. In felting a layer of these fiber bundles as described it has been found that the thinner the felt layer the more slowly the felting surface must run due to the fact that the thin wet felt leaving the machine is fragile. A

further reason causing a low rate of production of a thin felt lies in the fact that the rate of fiber deposition must be low since for thin layers the higher the rate of deposltion the greater the tendency to uneven deposirate of production is low.

Production on a single roll or wire machlne can be greatly accelerated even if a thin finalproduct, say /m" to thick is required. By felting to a thickness such as to produce a board of thickness some multiple to the desired product, a machine can produce a greater volume of finished product 1n a given time because, as stated above, the felt produced is firmer and the rate of deposition can be higher. This thicker board when divided by a splitting machine produces a p luralit of sheets of the desired thin material, resu ting in an increased overall rate of production for the machine much greater than could have been obtained should' the thin product have been initially formed.

It is obvious that those skilled in the art tion and therefore for a uniform sheet the 5 knife splitter in a plane parallel to its wide may vary the details of construction as well as arrangements of parts without departing from the spirit of the invention and it is therefore not desired to be limited to the foregoing except as may be required by the claims.

What is claimed is 1. The production of a substantially non laminated felted fibrous sheet by splitting in a plane parallel to a felting surface a felted sheet of coarse fibered insulating board formed initially in a thickness greater than that of the sheet desired.

2. A base for linoleum comprising a relatively semi-rigid but resilient felted coarse fibered insulating material having a smooth surface produced as by knife-splitting a sheet of the felted coarse fibered insulating board material. 1

3. A linoleum base comprising a non laminous relatively semi-rigid but resilient felted course fibered insulating material hav ing a smooth surface produced as by knifesplitting a sheet of the felted coarse fibered insulating board material.

4. A flooring material in combination with a separate linoleum base the same comprising a non laminous relatively semi-rigid but re silient felted fibrous material the process of manufacturecompr1sing digestion and refining of a coarse fibered vegetable substance, the felting of the fibers into a relatively wide and thin sheet, the drying of the sheet and the subsequent splitting of the sheet with a face.

5. A linoleum base comprising a non laminated relatively semi-rigid but resilient felted material and comprising principally fiber bundles derived from bagasse and the like.

6. The method of manufacturing a relatively semi-rigid but resilient felted fibrous material through the disintegration and refining of plant growth to produce fiber bundles resilient and unsuitable for paper making, the heterogeneous arrangement of the fiber bundles into a spongy porous feltlike mass containing-an appreciable amount of Water, the drying of the felted mass forming a semi-rigid board-like product and the su sequent splitting of the mass with a knife to obtain the desired product.

7. The production of a product comprising a semi-rigid resilient felted fibrous material composed principally of fiber bundles of bagasse and the like, the fiber bundles prepared by a digestion and refining whereby the fiber bundles are strong, flexible and resilient as distinguished from the raw material which isbrittle and from paper making stock which is soft, weak and of no apprecible resiliency, the fiber bundles in dilute suspension in a liquid and deposited therefrom in heterogeneous arrangement as a continuous wet felt produced on a machine substantially of the single roll or single wire paper making type whereby on the application of pressure and of heat for drymg there will result a homogeneous continuous nonlaminous semi-flexible fibrous sheet.

8. A method of increasing production of felting machine of the type of paper making machines comprising the formation on the machine of a felt of coarse fibered insulating board of a thickness greater than that of the finished sheet desired and the subsequent operation of splitting the thick sheet into a plurality of thin sheets.

9. A method of increasing production of a continuous felting machine producing course fibered insulating board and comprising the continuous formation on the machine of a felt of a thickness greater than that of the finished product and thesubsequent separation of the thick sheet into a plurality of thinner sheets.

10. In combination with linoleum and as a base therefor an non-laminous felted sheet comprising fibers derived from sugar cane and the like.

11. An article of manufacture comprising a semi-flexible felted sheet of heterogeneously arranged fibers of bagasse like material, said sheet having normally a rough surface due to the felting action and a relatively porous interior structure due to the heterogeneous arrangement of the fibers, said sheet on one of its wide faces being smooth as formed by knife-splitting a sheet of said material having a thickness greater than the finished article of manufacture.

In testimony whereof we afiix our signatures.

TREADWAY B. MUNROE. ELBERT C. LATHROP. 

